Pump or motor device



June 29; 1965 M. M. HANN ETAL PUMP OR MOTOR DEVICE 2 Sheets-Sheet 1 Filed July 27, 1962 uvvmroxs: mm June 29, 1965 M. M. HANN ETAL 3,191,543

PUMP 0R MOTOR DEVICE Filed July 27, 1962 2 Sheets-Sheet 2 United States Patent O 3,191,543 PUMP R MOTOR DEVICE Melvin M. Ham and Russell L. Power, Rockford, Ill.,- zlrlssignors to Sundstrand Corporation, a corporation of linois Filed July 27, 1962, Ser. No. 212,964 12 Claims. (or. 103-162) This invention relates to fluid pressure translating devices of the reciprocatingtype and especially relates to hydraulic pumps or motors of the axial piston design. More particularly, this invention relates to themaintaining of sealing and force translating contact between members within such devices. i

Fluid pressure translating devices of the axial piston type are well known to the art to be often usable as: either pumps or motors. Such devices usually include a drive shaft which is associated with either a cylinder block or an inclined or inclinable cam plate to create relative rotational movement between the cylinder block and cam plate. The cylinder block includes a plurality of pistons in cylinders in annular array about the axis of the cylinder block. The pistons have inner ends disposed for reciprocation within the cylinders and outer ends adapted to bear against and transmit force to or receive force from the inclined cam plate. The cylinder block includes passages from each cylinder to an end of the block for association with inlet and outlet passages in a port member. The inlet and outlet passages of the port member communicate successively with the passages from the cylinders upon relative rotation of the cylinder block with respect to the port member. The cylinder block is positively biased toward the port plate by pressure under operation of the device and by mechanical means which supplements the operating pressure, e.g., during starting of the device.

Further, in operation of the fluid translating device, a substantial lateral force may be placed on the cylinder block by the reciprocating pistons tending to displace the cylinder block from the port plate and the mechanical means assist in maintaining the cylinder block upon the port plate.

However, it is also highly desirable to maintain force transmitting contact between the reciprocating pistons and the inclined cam plate. -It has been proposed to utilize a single spring means reacting between the cylinder block and the piston bearing members to maintain not only contact of the piston bearing members with the cam plate but also contact of the cylinder block with the port plate. However, in some designs of fluid translating devices it has been found that the force necessary to maintain the piston bearing members in contact with the cam plate is much greater than that necessary to maintain the cylinder block in contact with the port plate. Thus, the single spring arrangement can, often require the use of stronger spring means throughout the span between piston bearing members and cylinder block than would otherwise be required, in some designs constituting an economical disadvantage and leading to unnecessary friction, wear and loss of efliciency. Additionally, prior art devices employing the single spring may be extremely ditlicult to assemble against the urging of the very strong spring.

It is a general object of this invention to provide new and useful means in a fluid translating device for biasing the cylinder barrel against the port plate and for biasing the pistons toward the cam plate.

It is a more particular object of this invention to provide separate spring means for biasing the cylinder block and the pistons, which spring means are both-grounded to a drive shaft in a hydraulic fluid translating device.

It is another object to provide such separate spring means wherein the spring means biasing the pistons comprises an annular series of compression'spring means recessed in the cylinder block and wherein the spring means biasing the cylinder block comprises a coil spring means disposed about the drive shaft, both of said spring means acting against said drive shaft.

A more particular object is to provide an axial piston hydraulic pump .or motor device having a housing, a rotatable cylinder block mounted in the housing, an annular series of axially disposed cylinders within the cylinder block, a series of pistons having inner ends reciprocating within the cylinders, a drive shaft rotatably mounted in the housing and drivingly connected to the cylinder block for rotational movement with the cylinder block, a cam plate mounted in the housing at one end of the cylinder block for pivotal movement about an axis transverse to the axis of the drive shaft, the cam plate having a bearing surface inclined to one end of the cylinder block, the pistons having their outer ends equipped with bearing means universally mounted on the pistons and slidably engaging the cam plate, the engagement of the piston bearing means with the cam plate or a bearing face thereof being maintained by a hold-down ring which engages the piston bearing means and which is engaged by a spherical collar slidably splined to the drive shaft and having its spherical center located at the approximate mid-point of the driving connection between drive shaft and cylinder block and falling upon the axis of the drive shaft at the point where the drive shaft axis pierces the plane containing the pivot points of the universally mounted bearing means, wherein there isprovided a first spring means in recesses in the cylinder block engaging the spherical collar and grounded against the drive shaft to maintain the piston bearing means on the cam plate, and there is further provided a second spring means which acts against the drive shaft and the cylinder block to urge the cylinder block against the motor or pump port or valve plate.

Further objects of this invention include the provision of fluid translating devices in accordance with the foregoing objects wherein there are provided means for grounding the spring means to the drive shaft and a particular arrangement of such spring grounding means.

Still other objects will become readily apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a longitudinal section, taken along line 1-1 with respect to FIG. 3, ofra hydraulic fluid translating device incorporating an embodiment of the present invention;

FIG. 2 is a longitudinal section, taken along line 22 with respect to FIG. 3, of the device illustrated in FIG. 1;

FIG. 3 is a partial section taken along line 33 0 FIG. 2; and 1 FIG. 4 is a partial section taken along line 44 of FIG. 2.

Turning now to the figures, the embodiment illustrated is incorporated in a pump or motor of the axial piston type. The motor includes a housing indicated generally at 10, having an end plate 11 removably secured thereto by suitable screw or bolt means 110. Drive shaft 12 is rotatably supported at one end of housing 10 by mounting bearings 16 and extends through cylinder block 14 to end plate 11 where the drive shaft is secured by press fit within race 15a of mounting bearing 15 abutting end plate 11. If desired, the press fit may be omitted and bearing 15 retained solely by contact with 'end plate 11. Bearings 15 and 16 secure drive shaft 12 against axial movement.

Drive shaft 12 is drivingly connected as by splines 13 V and drive shaft 12 together.

'tocylinder block'14 for rotation of cylinder block 14 includes cooperating splines on the drive shaft and cylinder block through which the drive shaft passes, and the splines are slightly crowned longitudinally to permit tilt- .ing of the cylinder block at the splined connection, which allows for irregularities in the rotation of the cylinder block.

Cylinder block 14 includes pistons, two; of which are shown-at 21. and 22 having inner ends 2111 and 22a reciprocating within bores or cylinders 23 and 2 1 in cylinder block 14. Cylinders 23-and 24 are provided with bearing inserts or bushings 25within which the pistons reciprocate. Although. only two pistons are shown in any one view in the figures, it is to be, understood that cylinder block 14 includes an annular plurality of axially disposed cylinders within the cylinder block, each cylinder having-an inner end of a piston reciprocating therein. 'Although it will be apparent from the discussions below that there are nine pistons in the annular series in the illustrated embodiment, any number of pistons and cylinders may be used, as is known to the art.

.Cam plate '31 is mounted within housing 10 at one end of cylinder block 14- for pivotal movement about an axis transverserto. and intersecting the axis of the drive shaft. The. pivotal mounting of cam plate 31 is provided by trunnions secured to housing 10 and indicated generally at'28 and 23. The cam plate is adapted to be pivoted about its axis at an incline in either direction with respect to a neutral central position for adjustment of displacement of the pistons asat 21 and 22 within the cylinder block cylinders, For this purpose projection on cam. plate 31 .is provided to pivot the cam plate on its axis. The projection is accessible through opening 10a in the wall of housing 10 and may be linked to suitable 'actuatingmeans connectible by-means of bore 330 to control the inclination of camplate 31 as disclosed, for example, in the copending application of Hann et al., Serial No. 95,078, filedMarch 13, 1961, now Patent No. 3,126,707 and assigned to the assigneeof this application.

The outer ends 21b and 2212.01 pistons 21 and 22 are of spherical configuration and are universally connected to bearing members such as bearing shoes 33 and 34 which'are adapted to slide upon an annular cam plate, thrust bearing member or surface 32 which is supported on cam plate 31. vOf course, other pistons within the motor are equipped with similar bearing shoes and wherever pistons. 21 and 22 are described in association withxother members, it is to be understood that the re- M mainder of thepistons are inassociation with similar or the same members, as vwillbe obvious to thosev in the art from the descriptions herein.

-' 'A.hold-down'member, such asring 35, engages the bearing shoes 33 and 34 and carries the bearing shoes in slidable contact with bearing surface32. Hold-down ring." 35 is provided with a spherical bore 35a which is engaged by and receivesthe spherical outersurface 36a of a spherical collar 36. Spherical collar 36 is splined at 131; for rotation withand axial'movement relative to shaft 12. The collar is slidable on and piloted by cylindrical-projection Maof cylinder block 14 for axialmovementoflc0llar36'withrespect to the block 14 and shaft 12. Collar 36 is adapted :to urge hold down ring 35 toward the bearing surfaceof cam plate 31, thereby urging thebearing shoes againstthe bearing surface.

' -An.auxiliary piston return is provided byannularshim 55, Iillustrated .in- FIGS.. 1- and 2 as a crushed or bent Washer and-will be described more particularly hereinbelow. Spherical collar 36 is spaced longitudinally along shaft 12;.from cylinder block 14 by means of shim Whichis-interposed between spherical collar 36 and cylinder block 14. Shiml55 acts as a stop to. prevent longitudinal abutment of the cylinder block and spherical collar. Y

The splined connection 13V and is provided during assembly of the device.

In order to maintain bearing shoes 33 and 34 against bearing surface 32, a first spring means,.such as an annular series of compression springs 37 and 33, interposed between the cylinder block cylinders, is provided. Compression springs 37 and 38 are grounded to drive shaft 12 through annular collar 41 and bias the spherical collar 36, carrying hold-down ring 35 in the direction of camplate 31, thereby urging shoes 33 and 3 1 against the bearing surface 32. Compression springs '37 and 38 extend through recesses 39 and-40 in-cylinder block 14 and are seated against the annular collar 41 and against spherical collar'fiange 36b.

Although compression springs 37 and 33 may be disposed parallel to the axis of shaft 12, it is preferred that thesprings be angularly disposed, such as illustrated in FIG. 1, to permit a heavier cylinder wall over more of the length of the cylinders and to provide a relatively longer spring cavity.

More particularly with respect to shim 55, the shim functions to maintain bearing members 33 and '34 in close proximity with the bearing surface 32 of'cam plate 31 without. respect to the urgingof springs 37 and 38.

Thus, if springs 37 and 38 should become overpowered during operation of the device, e.g., by sticking of pistons within cylinder block cylinders or by momentary sticking delay of the pistons being urged from the cylinders upon a rapid increase in torque, shim 55 prevents the withdrawal of the piston bearing. members from the cam plate a greater distance than a'minimum operating clearance. The minimum operating clearance is preselected Accordingly, as the elements are assembled from the left side of housing 10 and housing end plate 11 removed,

the spherical collar 36 is positioned, followed by an annularwasher and then cylinder block 14, etc. The annular .washer is sufiicient to cause the port plate 52 to abut housing endplate'11 before housing end plate 11 is peripherally secured in sealing relation with housing 10. As end plate 11 is drawn into sealing peripheral relation with housing 10, the end plate urges the cylinder block against the annular washer, thereby crushing the washer between the cylinder block and spherical collar to form shim 55. Housing end plate 11 is thereupon removed and a'gasket 18 of preselected thickness corresponding approximately to the minimum operating clearance, e.g., .0001, is positioned between housing end plate 11 and housing 10 and the housing end plate is replaced. in this manner, a minimumoperating clearance .0001 is provided between piston bearing members 33 and 34 and surface 32 and shim 55 prevents withdrawal of 'thepiston bearing members from the cam plate bearing surface a greater distance than the minimum operating clearance even under momentary overpowering of the piston return springs 37 and 38;

Annular collar 41 abuts annular shoulder 12a on drive shaft 12 and is held in abutment with the shoulder bymeansof annular sleeve 42 around drive shaft 12. Annular sleeve 42 in turn abuts race 15a of mounting bearing 15. Either annular sleeve 42 or'race 1Sa'is press fitted on shaft 12 to in effect anchor annular sleeve 42 against axial movement with respect to shaft 12.

A second spring means such as coil spring 43 is provided, reacting against annular collar 41. Coil spring 43 biases an annular collar 44, which is axially slidable on sleeve 42 or in'the cylinder block toward a'hardened port plate 52. Annular collar 44 abuts snap ring 45, which is secured to cylinder block 14, and thereby carries the snap ring and cylinder block toward port plate 52 under the urging of spring 43. A hardened bearing plate 51 pinned to the cylinder block at 51a rotates with the cylinder block extensions 51b of parts 23a therethrough. The passage configuration, as viewed from either side of plate 51 is the same as the passage configuration on the end of cylinder 14 as illustrated in FIG. 3. Plate 51 may include wear-resistant materials on its opposing surfaces and particularly on the surface facing port plate 52 or may be entirely of suitable bearing material such as bronze.

Port plate 52 includes arcuate inlet and outlet passages 11a and 11b passing therethrough for conducting fluid to and from passages 51b as cylinder block 14, including plate -51, rotates. The general configuration of passages on both sides of port plate 52 is generally the same and is also generally the same as the configuration of passages to the inner face of housing end plate 11 as illustrated in FIG. 4. Port plate 52 may also have wear-resistant surfaces, such as hardened steel, especially facing cylinder block end plate 51.

Inlet and outlet passages 1-1a and 11b extend through housing end plate 11 to an inlet and an outlet (not shown) in the usual manner. The inlet and outlet are connectible to fluid lines (not shown) for operation of the device as a pump or motor as will be readily apparent to those skilled in the art.

In the preferred application of the principles of the present invention, the spring means biasing the piston bearing members against the cam plate is adapted to exert a force upon the spherical collar approximately double the force exerted by the spring means acting to bias the cylinder block against the port plate, since it has been h found that the forces tending to separate the piston bearing members from the cam plate are approximately double those tending to separate the cylinder block from the port plate. For example, in one particular embodiment, spring means under compression and exerting a force of about 300 pounds is utilized to urge the piston bearing members against the cam plate while a coilspring exerting only about half that force, about 150 pounds or more, is used to bias the cylinder block against the port plate. But the force values may vary with variations in size of the pump or motor. For example, in a larger pump or motor a piston hold-down force of 860 pounds and a cylinder block biasing force of 400 pounds are provided.

In operation of the device as a motor, fluid valved through port plate 52 enters the piston cylinders on the high pressure side or inlet side of the port plate. The pistons 21 and 22 are urged to press bearing shoes '33 and 34 against the cam plate 31 which is inclined or inclinable by movement of projection 30 inthe usual manner to effect sliding of the shoes down the cam plate incline resulting in rotation of block 14 and shaft 12 splined thereto. The annular series of cylinder block passages are successively brought into association with the-high pressure or inlet passage of 11a and 11b and then with the low pressure or outlet passage in conventional manner as block 14 rotates. Also as the cylinder block rotates, bearing plate 51 slides against port plate 52 and is biased thereagainst by the force of pistons on the cam plate and by coil spring 43 which is grounded on the drive shaft. Additionally, shoes 33 and 34 slide around cam plate 31 on the cam plate bearing surface 32 and are urged against the bearing surface not only by the action of pistons 21 and 22 but also by compression springs 37 and 38 .grounded on the drive shaft and acting through spherical collar 36 and hold-down ring 35. Shim 55 prevents motor cannot remove the shoes more than the minimum operating clearance provided by the shim.

It will be apparent to those in the art that the device, although its motor operation has been described, is also operable as a pump. Accordingly, a prime mover is employed to rotate shaft 12 for conventional pumping action of an axial piston pump. Spring means 43 and spring means 37 and 38, both of which spring means are grounded on the drive shaft, independently act to bias block 14 toward the port plate and shoes 33 and 34 against the cam plate, respectively.

Regardless of its intended operation as a pump or as a motor, it is apparent that, in the present invention, there has been provided a new and useful improvement in a fluid energy translation device which employs the grounding of separate spring means against the drive shaft for maintaining the cylinder block and piston bearing members or surfaces in effectively operative association with the remainder of the motor or pump assembly even during adverse conditions of operation. It is an important advantage of the device of the present invention that the separate spring means are not subject to reversals of stress and function simply to supply a constant force biasing the cylinder block and piston bearing members into their proper association.

We claim:

1. An axial piston hydraulic fluid translating device comprising a housing, a rotatable cylinder block in said housing, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocable within said cylinders, a drive-shaft rotatably mounted in said housing, a driving connection between the cylinder block and drive shaft, a cam plate mounted in said housing at one end of said cylinder block and having a bearing face inclined to one end of the cylinder block, said pistons having outer ends, bearing means universally mounted on the outer ends of the pistons and having a bearing face engaging said cam plate, ports communicating the cylinders with the opposite end of said cylinder block, a port plate having inlet and outlet passages in the housing adjacent the opposite end of the cylinder block communicating successively with said cylinder ports upon rotation of the cylinder block, a holddown ring engaging said bearing means, and a spherical collar engaging the hold-down ring, the center of the spherical collar being located at the approximate midpoint of said driving connection and falling upon the axis of said shaft at the point where the shaft axis pierces the plane containing the pivot points of the universally mounted bearing means, first spring means in recesses in the cylinder block and engaging said spherical collar, a collar on said shaft against which the first spring means bears to maintain said bearing means on the bearing face, and second spring means acting against said collar and said cylinder block to urge said cylinder block against the port plate, whereby the springs act independently on the spherical collar and the cylinder block.

2. In an axial piston hydraulic fluid translating device, comprising a rotatable cylinder block, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocating within said cylinders, a rotatable drive shaft extending into said cylinder block, a universal connection between the cylinder block and drive shaft, a cam plate mounted at one end of said cylinder block for pivoted movement about an aromas ends, andta spherical collar engaging the hold-down ring, the center of saidspherical collar falling upon the axis of said shaft,'the improvement which comprises first compressiontspring means engaging said spherical collar and acting against said shaft to maintain the bearing means of the piston outer ends in engagement with said cam plate, second compression spring means acting against I said shaft and said cylinder block to urge said cylinder blocl; against the port plate, whereby the springs act independently'on the spherical collar and the cylinder block,

including a housing, a rotatable cylinder block mounted .in said housing, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocating within said cylinders, a drive shaft rotatably mounted in said housing extending into said cylinder block, a' driving connection between the cylinder block and drive shaft, bearing means in said housing restricting said drive shaft against axial movement, a

cam plate mounted in said housing at one end of said cylinder block for pivoted movement about an axis transverse to the axis of said drive shaft, said cam plate having a bearing face inclinedto one end of the cylinder block, said pistons having outer ends, bearing means universally mounted on the outer ends of the pistons and engaging said cam plate, ports communicating the cylinders with the opposite end of said cylinder block, a port plate having inlet and outlet passages adjacent the opposite end of the cylinder block communicating successively with said cylinder ports upon rotation of the cylinder block, hold-down means engaging said bearing means and a spherical collar engaging the hold-down means, the center of the spherical collar falling upon the axis of'said shaft at the point where the shaft axis pierces the plane containing the centers of the universal mountings of said outer piston ends, the improvement which comprises spring means in recesses in the cylinder block v said spring means engaging said spherical collar, a collar on said shaft against which the spring means bears to maintain said bearing shoes on said cam plate and second spring means acting against said collar and said cylinder block to urge said cylinder block against the port plate, whereby the springs act independently on the spherical collar and the cylinder block.

4. An axial piston hydraulic pump or motor device comprising a housing, a rotatable cylinder block mounted in said housing, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocating within said cylinders, a drive shaft rotatably mounted in said housing extending through said cylinder block, a spline connection between the cylinder block and drive shaft, bearing means in said housing restricting said drive shaft against axial movement, a cam plate mounted in said housing at one end of said cylinder block for pivoted movement about an axis transverse to and intersecting the axis of said drive shaft, said cam plate having a bearing face inclined to one end of the cylinder block, said pistons having spherical'outcr ends,

a series of shoes universally mounted on the spherical outer ends of the pistons and having a bearing face engaging the bearing face on said cam:plate, ports communicating the cylinders with the opposite end of said cylinder block, a port plate in the housing having inlet and outlet passages adjacent the opposite end of the cyltinder block communicating successively with said cylinder ports upon rotation of the cylinder block, a hold-down ring carryingsaid bearing shoes, a spherical collar en- "gaging the hold-down ring, the" spherical center of the spherical collar being located at the approximate midpoint of said spline and falling upon the axis of said shaft at the point where the shaft'axis pierces the plane containing the centers of' the spherical piston ends, an annular series of compression springs in annular recesses-interposed between cylinders in the cylinder block, said springs engaging said spherical collar at one end of said springs, a collar on said shaft against which the other ends of said springs bear to maintain said bearing shoes on said cam plate upon inclination of said swashplate relative to said shaft axis and a coil spring acting against said collar mounted on said shaft and against a snap ring bearing against said cylinder block to urge said cylinder block against the port plate, whereby the springs act independently on the spherical collar and the cylinder block.

5. In an axial piston hydraulic fluid translating device including a housing, a rotatable cylinder block mounted in said housing, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocating within said cylinders, a drive shaft rota-tably mounted in said housing extending into said cylinder block, a driving connection between the cylinder block and drive shaft, bearing means in said housing restricting said drive shaft-against axial movement, a cam plate mounted in said housing at one end of said cylinder block for pivoted movement about an axis transverse to the axis of said drive shaft, said cam plate having a hearing face inclined to one end of the cylinder block, said .pist-ons having outer ends, bearing means universally mounted on the outer ends of the pistons and engaging said cam plate, ports communicating the cylinders with the opposite end of said cylinder block, a port plate having inlet and outlet passages adjacent the opposite end .of the cylinder block communicating successively with said cylinder ports upon rotation of the cylinder block,

hold-down means engaging said bearing means and a H spherical collar splined .to said drive shaft adjacent said driving connection for rotation with and axial movement with respect to said shaft, said shaft engaging the holddown-means, the center of the spherical collar falling upon the axis of said shaft at the point where the shaft axis pierces the plane containing the centers of the universal mountings of said outer piston ends, the improvement which comprises pilot means comprising a cylindrical hub extension of said one end of said cylinder block, said spherical collar being slidably mounted on said hub extension for axial movement with respect to said cylinder block, an annular series of compression spring means in annular recesses in the cylinder block, a collar on said shaft againstwhioh the spring-means bears, said spring means being disposed angularly outwardly from said shaft with respect to-the axis of said. shaft and engaging said spherical collar radially from said hub extension to maintain said bearing'shoes on said camplate, and second spring means acting against said collar and said cylinder block to urge said cylinder block against the port plate, whereby the springs act independently on the spherical collar and the cylinder block.

6. In an axial piston hydraulic fluid translating device including a'h-ousing having a removable end plate, cylinder block rota-tably mounted in said housing, an annular series of axially disposed cylinders within said block, a series of pistons having inner ends reciprocating within said cylinders, a drive shaft rotatably mounted through mounting hearings in said housing and extending into said cylinder block and mounted through mounting bearings carried by said end plate, said drive shaft being univer'sally connected to said cylinder block, a cam plate 'mounted in said housing at one end of said cylinder block for pivoted movement about an axis transverse to the -axis of said drive shaft, saidv cam plate having a bearing face-inclined to "one end of the, cylinder block, said pistons having outer ends, bearing shoes *universally mounted on the outer ends of the pistons and engaging the bearing face of said cam plate, ports communicating the cylinders with the opposite end of said cylinder lock, a port plate between said end plate and said opposite end of the cylinder block, inlet and outlet passages in said port plate adjacent the opposite end of the cylinder block adapted to communicate successively with said cylinder ports upon rotation of the cylinder block, said inlet and outlet passages extending through said end plate, a hold-down ring engaging said bearing shoes and a spherical collar engaging the hold-down ring, the improvement which comprises a spline connection between the drive shaft and spherical collar, an annular series of compression springs in bores in said cylinder block extending from said spherical collar to a first annular collar surrounding said drive shaft and abutting an annular ridge on said drive shaft, a sleevesurrounding said drive shaft and extending from said first annular collar to abut the rotatable race of the drive shaft mounting bearing press fitted on said drive shaft, said sleeve being thereby grounded on said shaft and being adapted to maintain said first annular collar in abutment with said annular ridge, a second annular collar disposed about said sleeve and axially slidable on said sleeve, a coil spring disposed about said sleeve and engaging said first annular collar and said second annular collar for urging said collars in opposite directions, a snap ring on said cylinder block engaged by said second annular collar to urge said cylinder block against the port plate and compression spring means in recesses in said cylinder block, bearing between said first annular collar and said spherical collar and urging said spherical collar to maintain said hearing shoes in engagement with said bearing face of said cam plate, and annular shim means around said drive shaft between said cylinder block and said spherical collar spacing said spherical collar from said cylinder block adjacent said spline connections establishes a minimum running clearance between said bearing shoes and the bearing face of said cam plate.

7. In a hydraulic fluid translation device including bearings for a drive shaft immovable with respect to the drive shaft adapted to drive or be driven by a rotatable cylinder block having a plurality of pistons with inner ends disposed for reciprocation within cylinders in the block and having an inclined cam plate with a bearing surface against which piston bearing means carried by the outer ends of the pistons are urged in one direction and wherein the cylinder block is urged in another direction against a port member having inlet and outlet passages communicating successively with ports from said cylinders upon rotation of the cylinder block, the improvement in means for said urging which includes first spring means grounded against one of said bearings and urging said piston bearing means toward said cam plate and second spring means grounded on said drive shaft and urging said cylinder block toward said port member, and means for preventing axial movement of the shaft in either direction whereby the spring means act independently on the bearing means and the cylinder block.

8. In an axial piston pump or motor device, housing means, a rotatable cylinder block in said housing means having a central recess for receiving a drive shaft connectible for rotation with the cylinder block, bearing means in said housing constraining axial movement of said shaft in either direction, an annular series of pistons having inner ends reciprocable Within said cylinders, a cam plate at one end of said cylinder block having a bearing face inclined to the end of the cylinder block, second bearing means on the outer ends of the pistons engaging said cam plate, ports communicating the cylinders with the opposite end of said cylinder block, a port plate having inlet and outlet passages adjacent the opposite end of the cylinder block communicable successively with said cylinder ports upon rotation of the cylinder block, first spring means acting against said second bearing means to maintain said bearing means in engagement with said cam plate, and second spring means acting against said cylinder block to urge said cylinder block against the port plate, and means fixed with respect to said drive shaft and engaging said first and second spring means for grounding both spring means without transferring the force of one spring to the other whereby the springs act independently on the second bearing means and the cylinder block.

9. The device of claim 8 wherein said first spring means is of suflicient strength to exert a force upon said second bearing means approximately double the force exerted by said second spring means acting against said cylinder block.

10. The device of claim 8 wherein said grounding means includes an annular collar surrounding and fixed with respect to said shaft, and said cam plate being pivotally mounted in said housing means to vary the displacement of the device.

11. The device of claim 10 wherein said annular collar is secured between a shoulder on said drive shaft and an annular sleeve on said drive shaft secured against axial movement.

12. The device of claim 11 and further including holddown means between said second bearing means and said first spring means, said hold-down means being splined to said shaft and axially slidable with respect thereto, said first spring means comprising an annular series of compressing springs disposed angularly outward from said drive shaft in annular recesses in the cylinder block and engaging said hold-down means adjacent said cylinder block.

References Cited by the Examiner UNITED STATES PATENTS 2,543,624 2/51 Gabriel 103-162 2,776,629 1/57' Keel 103162 3,089,426 5/63 Budzich 103l62 FOREIGN PATENTS 855,582 12/60 Great Britain.

ROBERT M. WALKER, Primary Examiner.

LAURENCE V. EFNER, Examiner. 

1. AN AXIAL PISTON HYDRAULIC FLUID TRANSLATING DEVICE COMPRISING A HOUSING, A ROTATABLE CYLINDER BLOCK IN SAID HOUSING, AN ANNULAR SERIES OF AXIALLY DISPOSED CYLINDERS WITHIN SAID BLOCK, A SERIS OF PISTONS HAVING INNER ENDS RECIPROCABLE WITHIN SAID CYLINDERS, A DRIVE SHAFT ROTATABLY MOUNTED IN SAID HOUSING, A DRIVING CONNECTION BETWEEN THE CYLINDER BLOCK AND DRIVE SHAFT, A CAM PLATE MOUNTED IN SAID HOUSING AT ONE END OF SAID CYLINDER BLOCK AND HAVING A BEARING FACE INCLINED TO ONE END OF THE CYLINDER BLOCK, SAID PISTONS HAVING OUTER ENDS, BEARING MEANS UNIVERSALLY MOUNTED ON THE OUTER END OF THE PISTONS AND HAVING A BEARING FACE ENGAGING SAID CAM PLATE, PORTS COOMMUNICATING THE CYLINDERS WITH THE OPPOSITE END OF SAID CYLINDER BLOCK, A PORT PLATE HAVING INLET AND OUTLET PASSAGES IN THE HOUSING ADJACENT THE OPPOSITE END OF THE CYLINDER BLOCK COMMUNICATING SUCCESIVELY WITH SAID CYLINDER PORTS UPON ROTATION OF THE CYLINDER BLOCK, A HOLDDOWN RING ENGAGING SAID BEARING MEANS, AND A SPHERICAL COLLAR ENGAGING THE HOLD-DOWN RING, THE CENTER OF THE SPHERICAL COLLAR BEING LOCATED AT THE APPROXIMATE MIDPOINT OF SAID DRIVING CONNECTION AND FALLING UPON THE AXIS OF SAID SHAFT AT THE POINT WHERE THE SHAFT AXIS PIERCES THE PLANE CONTAINING THE PIVOT POINTS OF THE UNIVERSALLY MOUNTED BEARING MEANS, FIRST SPRING MEANS IN RECESSES IN THE CYLINDER BLOCK AND ENGAGING SAID SPHERICAL COLLAR, A COLLAR ON SAID SHAFT AGAINST WHICH THE FIRST SPRING MEANS BEARS TO MAINTAIN SAID BEARING MEANS ON THE BEARING FACE, AND SECOND SPRING MEANS ACTING AGAINST SAID COLLAR AND SAID CYLINDER BLOCK TO URGE SAID CYLINDER BLOCK AGAINST THE PORT PLATE, WHEREBY THE SPRINGS ACT INDEPENDENTLY ON THE SPHERICAL COLLAR AND THE CYLINDER BLOCK. 